GB2079888A

GB2079888A - Clutch control system

Info

Publication number: GB2079888A
Application number: GB8119504A
Authority: GB
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1980-07-08
Filing date: 1981-06-24
Publication date: 1982-01-27
Also published as: EP0043660A2; GB2079888B; EP0043660A3; EP0043660B1; BR8104327A; SU1237073A3; DE3174453D1; ES8204101A1; AU7194681A; MX149734A; JPS646050B2; ES503723A0; US4418810A; AU543540B2; JPS5747222A

Description

1

GB 2 079 888 A 1

SPECIFICATION Clutch control system

This invention relates to clutch control systems

* for the automatic control of the engagement of a . 5 motor vehicle friction clutch driven plate with a driving member on take up from a standing start. . According to this invention there is provided a vehicle transmission clutch control system comprising an electrical reference signal 10 generator, an engine speed sensor which produce a signal indicative of engine speed, a throttle position sensor which produces a signal indicative of throttle opening and which is combined with the engine speed signal to form a modified engine 15 speed signal, a comparator receiving the modified engine speed and reference signal to produce an error signal, and a clutch position control operated by the error signal to vary the state of engagement of the clutch to equalise said modified engine 20 speed signal and reference signal.

Preferably the throttle signal is an inverse relationship with the throttle opening so that at light throttle openings the signal is at a maximum and at full throttle the signal is at a minimum. 25 The invention will be described by way of example and with reference to the following drawings in which:—

Fig. 1 is a schematic drawing of a clutch control system according to this invention;

30 Fig. 2 is a detailed circuit of an engine speed sensor as is used in Fig. 1;

Fig. 3 is a detailed circuit of a limiter and trigger circuit as utilised in Fig. 1;

Figl 4 is a detailed circuit of a phase gain 35 shaping network utilised in Fig. 1;

Fig. 5 is a detailed circuit of the oscillator of Fig. 1;

Fig. 6 is a detailed circuit of the mark space ratio modulator of Fig. 1;

40 Fig. 7 is the output as used in Fig. 1; and

Fig. 8 is a graph of engine torque vs. engine speed.

The motor vehicle engine speed is sensed by a sensor 11 that produces a voltage V, proportional 45 to engine speed. The detailed circuit of the sensor is shown in Fig. 3 and is basically a magnetic probe sensing the teeth on the engine flywheel and a transistor pump. The sensor is connected to a comparator 13 which also receives a reference 50 signal VR from a reference signal generator 14.

This can be, for example, a potentiometer across

* the vehicle battery so that the reference voltage is » the same as a signal obtained from the sensor 11

at a particular engine speed e.g. 1000 r.p.m. 55 A throttle position transducer 15 in the form of a variable potentiometer produces a signal VT representative of throttle opening. The signal VT is made proportional to throttle closure i.e. at light throttle openings the signal is at a maximum and 60 at full throttle openings the signal VT has a minimum value. This relationship can be written as VT = k (1 — throttle opening). This inverse relationship between the signal VT and the throttle opening is utilised because the signal VT is

65 required in this form to control other functions in the vehicle gearbox. The throttle position transducer 15 is connected to a limiter 28, the action of which is to allow the signal VT to vary only over a limited range say 10%—50% of 70 throttle opening. The limiter 28 is shown in detail in Fig. 3. The signal VT is fed into the engine speed signal V, to form a modified engine speed signal V{.

The comparator 13 receives the modified 75 reference signal V] for comparison with the reference signal VB and produces an error signal E which is fed into a clutch position control which controls the operation of an actuator 137. The actuator 137 operates the vehicle clutch 131 and 80 is powered by hydraulic pressure but could alternatively be pneumatic or electrical.

The clutch position control comprises a comparator 130 that receives the error signal E and a feed back signal Vp from a travel transducer 85 132 responsive to the position of the clutch. The feed back signal Vp is representative of the position of the clutch. The signal derived from the comparator 130 is fed into a phase gain shaping network 133, a mark space ratio modulator and 90 oscillator 134 and 135, respectively, and is then utilised via output 138 to control a solenoid operated hydraulic valve 136. The hydraulic valve 136 controls hydraulic flow through the hydraulic actuator 137. The mark/space ratio of the signal 95 fed into the solenoid valve 136 determines the hydraulic flow into the actuator and hence the rate of engagement of the clutch driven plate with its driving member. The shaping network 133, oscillator 135, mark/space ratio 134 modulation 100 network and output 138 are shown in detail in Figs. 4—7 respectively.

The actuator 137 operates so as to equalise the feed back signal Vp with the error signal E. Consequently the actuator 137 takes up a position 105 dictated by the error signal E and which is proportional to the value of the error signal E.

A comparator trigger circuit 23 is connected between the reference signal VR and the modified engine speed signal VI. The trigger circuit actuates 110 when (V, + VT) > VR and it modifies the throttle signal VT with an output signal Vx as described hereinafter.

The clutch position control operates the actuator 137 during clutch take up to vary the 115 state of engagement of the clutch driven plate with driving member on the vehicle engine (not shown) and thereby alter the engine speed to cause the modified engine speed signal V] to approach equivalence with the reference signal VR 120 and make the error signal E approach zero, when the signal V{ is lower than the reference signal VR the clutch is disengaged, and when the signal V] exceeds VR the error signal changes its polarity and the clutch loads the vehicle engine to cause 125 the engine speed to decrease and make V] = VR at which point the error signal tends to approach zero.

Hence for a given throttle opening during clutch tak^up the clutch engagement will arrive at the

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GB 2 079 888 A 2

condition where V} = V„. Once the clutch is fully engaged the engine speed can rise above the reference and the clutch control will hold the clutch fully engaged.

5 From a standing start with the vehicle engine idling VR is equal to some constant value, say 11 volts, and therefore, since V, is very iow, V] is just less than V„ and the clutch is fully disengaged. As the driver increases the throttle opening the 10 engine speed increases and V, causes the signal VJ to equalise VR at say 1000 r.p.m., the error signal E goes to zero, and the clutch control begins to engage the driven plate with vehicle engine driving member.

15 Now with the vehicle stationary, as the throttle is opened to make the vehicle move off VT gets smaller and hence the engine speed signal V,

must be higher before the clutch begins to engage. This causes the engine speed to become 20 higher before the clutch engages. Therefore if the vehicle is under load on a hill then the clutch will not engage until the engine has developed enough torque to accelerate the load. With reference to Fig. 8 the graph shows the torque output against 25 engine speed curves for various throttle openings. The line A represents a fixed take up speed and the line B represents the take up speed being variable with throttle opening, therefore allowing greater torque output from the engine at the 30 clutch engagement.

On vehicle take-off, initially when the clutch is disengaged the modified signal V{ is below the reference signal V„ so that the trigger circuit 23 receives a low input signal and the trigger circuit is 35 dormant and is isolated from the throttle signal VT by a diode 33. When the clutch engagement is complete and V] exceeds VR the trigger circuit is energised and its output Vx goes positive so that this pulls the throttle signal VT up to a value similar 40 to that of a light throttle value. This is accomplished via diode 33. The effect of this is that if the engine load increased after *

synchronisation e.g. on a hill start, the clutch will-not slip until the engine speed drops below the 45 original engagement speed. *

Claims

1. A vehicle transmission clutch control system comprising an electrical reference signal generator, an engine speed sensor which produce 50 a signal indicative of engine speed, a throttle position sensor which produces a signal indicative of throttle opening and which is combined with the engine speed signal to form a modified engine speed signal, a comparator receiving the modified 55 engine speed and reference signal to produce an error signal, and a clutch position control operated by the error signal to vary the state of engagement of the clutch to equalise said modified engine speed signal and reference signal. 60

2. A system as claimed in Claim 1, wherein the throttle signal is an inverse relationship with the throttle opening so that at light throttle openings the signal is at a maximum and at full throttle the signal is at a minimum.

65

3. A system as claimed in Claim 1 or 2, wherein a comparator trigger circuit is connected between the reference signals and modified engine speed signal so that when the trigger circuit is energised by a predetermined imbalance between the two 70 signals the trigger circuit output signal is fed into the throttle position sensor signal.

4. A system substantially as described herein and as illustrated in the accompanying drawings.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1982. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.